1. Field of the Invention
The present invention relates to a technology for injecting an object into a cell with a needle.
2. Description of the Related Art
A study of an alteration of genetic information of a cell by running a microscopic needle into the cell and injecting a gene, using a microscope clarifies a role of the gene and permits a tailor-made medicine of conducting gene treatment in accordance with individual genetic characteristics. Such study has made it possible to cure illness attributable to genetic causes that have heretofore been incurable.
The methods for injecting a gene into the cell can be, e.g., an electric method (electroporation), a chemical method (lipofection), a biological method (vector method), a mechanical method (microinjection), etc.
Among those methods, the electrical method includes breaking the cell membrane by running a large current, giving a big damage to the cell. The chemical method is limited in the number of genes to be introduced and is poor in respect of introduction efficiency. The biological method has the defects such as that it there is a limitation on the number of materials to be introduced and that safety of this method cannot be confirmed.
As a result, at present, in many cases, the mechanical method is employed as the safest and the most efficient method. For example, Japanese Patent No. 2624719 discloses a technology regarding the microinjection apparatus that arranges cells in regular order and automatically performs the microinjection.
The conventional technology represented by the above-identified patent, however, has the following problems. A first problem is that an experienced skill is required for a gene injection work because, due to the transparency of a cell as an object and a petri dish to which the cell adheres, the presence itself of the cell is not clear and the cell itself must be detected and must be shifted to an observation position, or a height of the cell or a border between the cell and the petri dish are difficult to judge and that since, due to one objective lens used at a microscope, three-dimensional feeling of the cell and the petri dish is difficult to grasp, work must be performed by alternately using a low magnification lens and a high magnification lens, resulting in inefficiency.
A second problem is that due to an inclination of a bottom surface itself of a petri dish, an absolute position of the cell in vertical direction varies depending on the position at which gene injection work is carried out, and therefore, a focal position of a microscope must be adjusted and a needle position must be adjusted, each time, resulting in inefficiency. There was a further problem that since the thickness and the inclination of the bottom surface of the petri dish are not uniform, varying from one petri dish to another, and the thickness and the inclination of the petri dish vary depending on a way of arranging the petri dish on a microscope stage, the focal position of the microscope must be adjusted and the needle position must be adjusted each time the petri dish itself is changed for another one or the way of arranging the petri dish on the stage is changed.
As a result, a method of placing a mark on the petri dish or a method of having the cell adhere to a cell catching plate on which a grid is drawn and arranging it within the petri dish were conventionally in use as a method of measuring the bottom surface, but these methods had a problem of contaminating the cell in placing the mark on the petri dish or of taking much trouble in preparing samples.
To solve the second problem, a method was devised of measuring the bottom surface using a dedicated optical system different from a system of observing the cell, but this method had a problem that a microinjection apparatus must have at least two lines of optical system, making a configuration of the apparatus complicated, or making the apparatus expensive or reducing the usability and maintainability of the apparatus.
The method of observing the cell conventionally was a differential interference method and a phase difference contrast optical system, but these methods, developed for making the cell more easily viewable in visual observation, had a problem that an edge of the cell is overemphasized, and therefore, were not suitable for an automation of the cell focal point adjustment.